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Open and close forms through a menu c#

I've had a look around but none of the answers make any sense to me. I have a menu form which has buttons on; when users come to use the menu form, you can open other forms from the menu. Currently, I can get the form to open, but the menu form stays open too.
private void BtnAddNewCar_Click(object sender, EventArgs e)
{
AddCompanyCar carForm = new AddCompanyCar();
carForm.ShowDialog();
}
The code above opens the form AddCompanyCar from the menu. How do I add to this code so that the form 'Menu' closes when AddCompanyCar opens?

Are you sure want to do this as it impacts usability. If you're using WinForms, then just create a container window, and replace the panels instead. Might be easy and best way
If not and you wanna go-ahead, can take a look on this example

Why not just hide it, then show it again when ShowDialog() returns?
private void BtnAddNewCar_Click(object sender, EventArgs e)
{
this.Visible = false;
AddCompanyCar carForm = new AddCompanyCar();
carForm.ShowDialog(); // execution stops here until "carForm" is dismissed
this.Visible = true;
}

by closing the main window, you destroy the context in which you were previously working. As others suggest, simply hide the main window so you can return to it.

Properties Window in C#

I'm currently trying to create a Properties Window which is opened after a Button on the Outlook Toolbar is pressed, i now have:
1) the Button on the Toolbar (currently if pressed nothing occurs)
2) i know how to create the method which would hold the action after the Button is Pressed
-but, I am a beginner and i don't know how to create a window which would open after the button is pressed, the Window should be fairly big, and for now have nothing but a checkbox(which i later would like to apply some method to.
if you ever created a window which opens after a button is pressed, i would be really pleased to get your help.
All help is appreciated, thank you

Here's the recommended way of opening a dialog window when the user clicks a button:
Add a new form to your project (e.g. MyForm) and then you can use the following code in your button's click event handler:
private void OnMyButtonClicked(object sender, EventArgs e)
{
MyForm myForm = new MyForm();
if (myForm.ShowDialog() == DialogResult.OK)
{
// The code that should be executed when the dialog was closed
// with an OK dialog result
}
}
In case you do not want the new window to be modal (i.e. you want to allow the user use other parts of the application while the window is opened), the code gets even more simple:
private void OnMyButtonClicked(object sender, EventArgs e)
{
MyForm myForm = new MyForm();
myForm.Show();
}
You can also create your form on the fly without adding one to your project, which is a bit more complicated, but advanced developers prefer this approach instead of messing with the designer ;)
private void OnMyButtonClicked(object sender, EventArgs e)
{
Form myForm = new Form();
myForm.Text = "My Form Title";
// Add a checkbox
CheckBox checkBox = new CheckBox();
checkBox.Text = "Check me";
checkBox.Location = new Point(10, 10);
myForm.Controls.Add(checkBox);
// Show the form
myForm.Show();
}

Here is a small tutorial for you to follow..
http://msdn.microsoft.com/en-us/library/ws1btzy8%28v=vs.90%29.aspx
EDIT: I would also recommend you remember the msdn website because it will prove invaluable for other programming issues you come across..

you have to add a new form to your project. Then you call the constructor where you want to pop up the window.
like this
Form2 form2 = new Form2();
form2.showDialog();
Edit:
where form2 is not the "main" Form of you program.
This'll set your main window to the background as long as the newly popped up window is closed.

Minimizing and restoring a form while showing another form

I have 2 forms, one of them is being showed through clicking a button in the first one. I want it such that when the button for showing 2nd form is clicked, first form gets minimized, and the second form opens normally. And when the 2nd form is being closed, the first window should become un-minimized and be placed where it was before.
User can override this and just click on the first form in quick luanch area and bring up the first form if he/she wants, so I dont want the 2nd from to me of Dialog kind.
I am trying the code below, but when I click on the button, the 1st form gets minimized, and also the second form is being minimized too! so I have to manually un-minimize 2nd form!
private void button1_Click(object sender, EventArgs e)
{
if (DebugForm != null)
return;
DebugForm = new DebugForm();
DebugForm.Closed += delegate
{
WindowState = FormWindowState.Normal;
DebugForm = null;
};
WindowState = FormWindowState.Minimized;
DebugForm.Show();
DebugForm.WindowState = FormWindowState.Normal;
DebugForm.BringToFront();
}

It seems to minimize both windows when there is another window on your screen. Minimize all windows except your application. You will see that it works. Keep it working along with other windows like this:
Change this:
WindowState = FormWindowState.Minimized;
DebugForm.Show();
DebugForm.WindowState = FormWindowState.Normal;
DebugForm.BringToFront();
to this:
DebugForm.Show();
WindowState = FormWindowState.Minimized;
The lines I removed weren't really necessary. The important thing is the order of statements to coordinate with the Z order of the parent form before minimizing it.

Ran into similar issue. The problem was that the form I was trying to call back was not an active form. Here's how I solved the issue. On the button click of the current from2 I added:
if (form1.ActiveForm == null)// Check to see if form is active
{
form1 frm = (form1)Application.OpenForms["form1"];// find open form
frm.WindowState = FormWindowState.Maximized;// Set state
frm.ShowInTaskbar = true; //set to show in taskbar
}

MDI application issues

General description of application:
Main form as MDI Container. On application start, if there is no xml file for database configuration (it is checked in Main form) Main form i call another form as showdialog() to fill all database info to build connection string. Then i close form and open another for login, then i get back to Main form, which has Split Container (2 panels: 1-menu on top, 2-content from child forms).
I open forms with:
private void PlanButton_Click(object sender, EventArgs e)
{
plan.TopLevel = false;
KontenerMenu.Panel2.Controls.Add(plan);
plan.Dock = DockStyle.Fill;
plan.Show();
}
and close form with:
private void Plan_FormClosing(object sender, FormClosingEventArgs e)
{
e.Cancel = false;
this.Hide();
}
Problems i have with app:
1. When i hit Cancel button when i open ShowDialog() form for database app crashes. Cancel button is simply:
private void cancelButton_Click(object sender, EventArgs e)
{
Application.Exit();
}
2. I have problem with clicking button to open/close/open again child forms. When i hit 'X' and want o open, app crashes with exception that it cannot refer to non-existing object
3. I have several buttons when i hit one and then another one it is always below the first one and not on the top
4. For example my form is 200x200 and in right down corner i have button (so location let's say 190x190) and i hit maximize button. My button is still on 190x190 and i would like to have it on down right corner. I couldn't find any property for that. Is there any or i have to write some code for that.

I'm not sure I understood your questions. Please make them clear.
But as an answer to question #4, there's an anchor property that does what you want.

Instead of trying to exit the application from within the dialog form itself you should return a DialogResult value and test that in the main form. The cancel button on the dialog doesn't need any code, just set its DialogResult property to 'Cancel' and if you have an Ok button set its DialogResult to 'OK'.
DialogForm f = new DialogForm();
DialogResult r = f.ShowDialog();
if (r == DialogResult.Cancel)
{
Close();
}

I can immediately see a number of problems with you code, including:
If you're going to add controls dynamically using Controls.Add, you should make sure the controls you're adding are dynamically created using new(). I get a sense that you don't have a clear understanding of object lifetimes and the WindowForms control life cycle.
The Application.Exit method should be used only in unusual cases. It's purpose is to achieve exactly the result you're observing - to immediately "crash" the application. The easiest way to have a button close a modal dialog is the set the DialogResult property of the button.
Winforms has a very elegant system for placement of control on a variable sized window. In order to use this system, you should familiarize yourself with the Anchor and Dock properties that are available on all controls.
It looks like what you're doing is attempting to learn WinForms by trial and error. You can do this, but it will take much longer and be much more painful that getting a hold of a good tutorial, book, or perhaps even attending a class if you can manage it. That will allow you to take these issues one at a time and have a much more enjoyable learning experience.

How to keep the focus back to form when clicking on OK button in windows forms?

I have a windows form with multiple controls and OK and Cancel buttons. In the Click event handler of OK button, it checks to see if there are errors on the form. I need the form to stay open if there are errors. But the code below is not working. If there are errors, it is closing the form and returning to the caller. And I have the below two lines to invoke and show the form.
PtForm paymentForm = new PtForm();
ptForm.ShowDialog();
private void btnOk_Click(object sender, EventArgs e)
{
this.ValidateChildren(ValidationConstraints.Visible);
string ErrorString = GetValidationErrors();
MessageBox.Show(ErrorString, "Errors");
if (!string.IsNullOrEmpty(ErrorString))
{
return;
}
//Processing
}
Thanks for any help.

There's nothing in this code that will close the form. Therefore, the culprit must be outside this code.
Did you set your OK button's DialogResult property to DialogResult.OK? That would explain why the form is closing. AFAIK, if you set DialogResult on the button, that's what happens -- there's no way to veto it in code.
So in that case, you would need to go back to the designer and set the button's DialogResult back to None. Then at the end of your btnOk_Click method, once you've validated all the input and decided that it's safe to close the dialog, add a line that sets your Form's DialogResult property to OK.

Remove DialogResult property of a button-i.e. set it to None.